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Interfacciamento porta parallela e primi esempi in Java Alessandro Memo.

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Presentation on theme: "Interfacciamento porta parallela e primi esempi in Java Alessandro Memo."— Presentation transcript:

1 Interfacciamento porta parallela e primi esempi in Java Alessandro Memo

2 Some basics of a parallel port A port contains a set of signal lines that the CPU sends or receives data with other components. We use ports to communicate via modem, printer, keyboard, mouse etc. In signaling, open signals are "1" and close signals are "0" so it is like binary system. A parallel port sends 8 bits and receives 5 bits at a time, with the use of three different registers.

3 Some basics of a parallel port Thus it is often called as printer Port or Centronics port (this name came from a popular printer manufacturing company 'Centronics' who devised some standards for parallel port). You can see the parallel port connector in the rear panel of your PC. It is a 25 pins female (DB25) connector (to which printer is connected). On almost all the PCs only one parallel port is present.

4 Some basics of a parallel port The IEEE 1284 Standard which has been published in 1994 defines five modes of data transfer for parallel port. They are: 1) Compatibility Mode 2) Nibble Mode 3) Byte Mode 4) EPP 5) ECP Typically, well use only Compatibility Mode.

5 D D1D2D3D4D5D6D7 S7S6S5S4S3S2S1S0 C7C6C5C4C3C2C1C0 DATA PORT CONTROL PORT STATUS PORT Some basics of a parallel port The parallel port contains three groups of bits: data bits (D 0 -D 7 ) status status (S 3 -S 7 ) control bits (C 0 -C 3 ) and ground bits (18-15)and ground bits (18-15) GND

6 Parallel Port – Data bits The old PC has LPT parallel port function only for sending data. Many devices nowadays have attached to this port and can work bidirectional (ECP and EPP mode). Data Port can sink 24 mA at logic 0 and can source 2.6 mA at logic 1. Notice that the external device don't try to pull these DP lines to ground for a long period. The latch IC could be burn.

7 pin num BIT SIGNAL NAME INPUTOUTPUT DATA PORT 0x D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 These bits may be input, but all you will get is the value currently residing in the output latch, unless the interface is genuinely bi-directional Latched TTL push-pull outputs with 2.2nF slow- down capacitors Parallel Port – Data bits

8 Parallel Port – Status bits Status Port use for feedback signal from printer to the computer. Only 5 MSB bits are used and accessible. Only 1 bit is inverting input, ie. S7, use for busy signal. S6 bit use for acknowledge signal, this signal used when the printing goes on with interrupt handshake operation. This is a hardware interrupt. In some PC/AT's card and bi-directional card, S2 is used to reflex the state of IRQ, weather it is on or off state. This bit only for internal use.

9 pin num BIT SIGNAL NAME INPUTOUTPUT STATUS PORT 0x na S7 S6 S5 S4 S3 S2 S1 S0 BUSY ACK PAPER_OUT SELECT ERROR IRQ not available TTL inputs no pull-up resistor not available Parallel Port – Status bits

10 Parallel Port – Control bits Control Port is used for controlling the function of printer. Only 4 bits used by printer and 1 bit used for interrupt enable flag. The most important things must be taken if you connect your own device are : the C0, C1 and C3 logic are inverting at socket connector terminal. This means that, when you send logic 1 (high) to this related bit, the logic output terminal is 0 (low). The C2 and C4 are normal. Note that, C4 bit only for the adapter card function.

11 Parallel Port – Control bits pin num BIT SIGNAL NAME INPUTOUTPUT CONTROL PORT 0x037A na C7 C6 C5 C4 C3 C2 C1 C0 not available DIRECTION IRQ ENABLE SLCT IN INIT LINE FEED STROBE not available may be used as inputs if corresponding output bits are set to "1 not available open collector output with 4.7K pull-up resistor and 2.2nF slow- down capacitor

12 Besides that, in some PC/AT's LPT adapter card, bit C5 is used for control direction (and also in bi- directional card). It means that, if this bit is high, Data Port can act as input port, the latch output is tri-state. Data from outside can be read from Data Port. Control Port can sink 7 mA at logic 0 and can source 0.6 mA at logic 1. Parallel Port – Control bits

13 Standard Interface Description LPT printer parallel interface in PC computer type have specification like this : Data transfer rate : 1000 cps (maximum) Synchronization : by externally-supplied STROBE pulses. Handshaking -ACK or +BUSY signals. Logic level : input data and all interface control signal are compatible with the TTL level.

14 Standard Interface Description

15 Checking LPT Installed In a new card (bidirectional card), simple send a byte to DP port and then read back again. If the result was not an FF Hex or if the result exactly the same to the byte wrote, then the card is installed at that port. This happened because, if the card not installed, the accessing port is a tri- state all, there is no connection to the hardware logic. Tri-state logic interpreted as logic 1.

16 Software - Java 1.Predisporre una cartella per ogni applicazione che si intende sviluppare, e copiare al suo interno i file pPort.class e ioPort.class 2.Copiare (se non è già presente) il file jnpout32pkg.dll nella cartella C:\WINDOWS\system32, oppure in alternativa copiarlo nella cartella dellapplicazione 3.Inserire nel programma la direttiva import jnpout32.*;

17 import jnpout32.*;// interfacciamento alla DLL public class minimo { static short dato;// variabili di classe static short indirizzo; static pPort lpt; public static void main ( String args[ ] ) { lpt = new pPort ();// istanza di una nuova porta indirizzo = 0x378;// indirizzo Data Port LPT1 dato = 0x77;// un dato qualsiasi lpt.output (indirizzo,dato);// scrivo il dato System.out.println ("Scrittura nel Port: " + indirizzo + " del dato: " + dato); dato = (short) lpt.input (indirizzo);// leggo il dato System.out.println ("Lettura dal Port: " + indirizzo + " del dato: " + dato); }

18 Methods of class pPort : ParallelPort output method: public void output (short port, short value) ParallelPort input method: public short input (short port) Set all bits on Data port to zero: public void setAllDataBits (short value) Set PinNumber to : public void setPin (short pin, short value) Definition and declaration of port: pPort = new pPort();

19 Extension of methods of class pPort : Set Data Bit at selected index to a value of 1 or 0 while preserving current values of all other Data bits: public void setDataBit (short index, short value) Set Control Bit at selected index to a value of 1 or 0 while preserving current values of all other Control bits: public void setControlBit (short index, short value) Get Status Bit at selected index to a value of 1 or 0: public void GetStatusBit (short index, short value) NB: attention to the type (short) !!!

20 dato_in = ((.input(STATUS_PORT)^0x80) >> 3);


22 The bi-directional card used bit C5 to control the direction of data in Data Port. If the C5 bit is low, the Data Port act as output port and if it is high, the Data Port is used for input port. When the Data Port act as output port, the data is latch at the output, so if we read this data back from the Data Port, the data must always the same as that we send. But if Data Port act as input port, the read data must be FF Hex, because the latch of Data Port is in tri-state. Checking LPT Bi-directional





27 Esercizi riepilogativi 1.Leggere lo stato di tutti i tasti 2.Individuare lo stato di un solo tasto (bit S6) 3.Accendere e spegnere dei LED (Data Port) 4.Ruotare i LED con una frequenza di 1 secondo 5.Ruotare i LED fino alla pressione di un tasto particolare 6.Accendere e spegnere tutti i LED del Data Port seguendo sequenze prestabilite associate ai vari tasti (proposto)

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